The ergonomics, the comfort in use of the control device by the operator, specifically by the pilot when the device is for an aircraft, are criteria that need to be taken into account when designing a device of this type. It is useful for the pilot to feel a force when handling the equipment, specifically for controlling the engine, on moving the throttle lever towards its maximum-actuation position. That is why the control device is generally designed to include friction brake means, which means are generally mechanical and serve to oppose in controlled manner the movements that are imparted to the control device by the operator, e.g. to the throttle lever by the pilot.
Such friction brake means may be systems that make use of a friction element, such as a friction pad, that rubs against an element secured to the control device, thereby opposing resistance to the force applied by the pilot to said device. Such friction systems are effective, they give a good sensation of force return to the operator, and they are reliable, however they are not without drawbacks: they wear over time, and therefore need to be replaced periodically, or at least to be verified. They are not completely insensitive to variations in temperature, they give the operator a feeling of friction that could be improved, and finally, their response depends on the speed with which the operator moves the control device.